Intermittent problem

LSter

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'04 LS V8. 94K. Just did plugs, coils, VCGs, and upstream bank 2 O2 sensor. When driving on the interstate and riding with the cruise control on, the car ever slow slightly hesitates while going downhill. Uphill, no problem. Just happens on cruise going downhill, doesn't matter what speed I'm going (which is usually 70). Any thoughts?
 
'04 LS V8. 94K. Just did plugs, coils, VCGs, and upstream bank 2 O2 sensor. When driving on the interstate and riding with the cruise control on, the car ever slow slightly hesitates while going downhill. Uphill, no problem. Just happens on cruise going downhill, doesn't matter what speed I'm going (which is usually 70). Any thoughts?

Sounds like normal operation. Mine do it too.
 
ETC 'feature' then?

I wouldn't call it a feature as much as I would call it the computer trying to hold a speed. Mine was most prevalent above ~60. Gearing has a lot to do with it.
 
some minor sht (like this sounds to be) is difficult to diagnose via internet. my question is did it do this before you did the maintenance described?

if it did not do it before the maintenance described, you can definately get rid of it. clear your KAM by disconnecting your battery and follow the battery reset procedure AND adhere to a quick drive cycle procedure. you may need to do this more than once as the PCM is highly adaptive the first time you start the car after unplugging your battery. just pull the batery cable and follow the procedure until your car shifts how you want it to shift (within its capabilities of course).

if it had the symptom described before your maintenance you are unlikely to fix it & rid yourself of it in my opinion unless you had major failures with the parts/maintenance described and drove around for an extended period with the parts out of spec AND failed to clear the KAM after replacing the parts and performing the maintenance...
 
jrand, you can't clear the KAM by simply disconnecting the battery.
I'm sure I already read this a few times in the workshop manual.
It said you have to go to the dealership for a special tool.


I have to read now again don't I ?

I will (again) but later.
 
jrand, you can't clear the KAM by simply disconnecting the battery.
I'm sure I already read this a few times in the workshop manual.
It said you have to go to the dealership for a special tool.


I have to read now again don't I ?

I will (again) but later.

you can on a genII. i cant say ive ever checked for a genI. just touch the positive and negative together for a couple mins and everything is gone.

shift strategies will go with just the negative and p1000 will be set
 
hmmm, interesting, for my GEN I

found:

Powertrain Control Module (PCM) Reset

Description
All OBDII scan tools support the powertrain control module (PCM) reset.

The PCM Reset allows the scan tool to command the PCM to clear all emission-related diagnostic information. When resetting the PCM, a DTC P1000 will be stored in the PCM until all the OBD II system monitors or components have been tested to satisfy a drive cycle, without any other faults occurring. For more information about a drive cycle, refer to Drive Cycles .

The following events occur when a PCM reset is performed:

Clears the number of Diagnostic Trouble Codes (DTCs).
Clears the DTCs.
Clears the freeze frame data.
Clears diagnostic monitoring test results.
Resets status of the OBD II system monitors.
Sets DTC P1000.


Resetting Keep Alive Random Access Memory (RAM)

Resetting Keep Alive RAM will return PCM memory to its default setting. Adaptive learning contents such as idle and fuel trim are included. A PCM Reset (described above) is also part of a KAM Reset.

After Keep Alive RAM has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.

This function may not be supported by all scan tools. Refer to scan tool manufacturer's instruction manual.

If an error message is received or the scan tool does not support this function, disconnecting the battery ground cable for a minimum of 5 minutes may be used as an alternative procedure.


I'll be damned!
had read something before on a different date that it couldn't be done and was a trip to the dealership.

but then again, when I replaced my MAF I went through this and it relearned.
 
if it had the symptom described before your maintenance you are unlikely to fix it & rid yourself of it in my opinion unless you had major failures with the parts/maintenance described and drove around for an extended period with the parts out of spec AND failed to clear the KAM after replacing the parts and performing the maintenance...

It did it before I did the maintenance. I thought it was due to the fact that one of my coils had become marginalized due to excessive oil in the plug well. Guess it's time to do the reset. Haven't had the time to do it until now.
 
It did it before I did the maintenance. I thought it was due to the fact that one of my coils had become marginalized due to excessive oil in the plug well. Guess it's time to do the reset. Haven't had the time to do it until now.

if it was mine and this was the only symptom it had: before i disconnected battery to reset the whole dam thing i would just do step 10 of the drivecycle procedure and another step which has to do with driving at like 60 and letting it coast down to 40 and then doing something... i dont remember exactly what the step says or which step # it is, but if you go searching you will see what i am talking about.
 
'04 LS V8. 94K. Just did plugs, coils, VCGs, and upstream bank 2 O2 sensor. When driving on the interstate and riding with the cruise control on, the car ever slow slightly hesitates while going downhill. Uphill, no problem. Just happens on cruise going downhill, doesn't matter what speed I'm going (which is usually 70). Any thoughts?

Is it holding the speed? If so, then that's just the cruise control doing its job.
 
like LS4me said, if this is only happening with the cruise on its normal operation as the car is attempting to maintain speed. No need to mess with anything.
 
Is it holding the speed? If so, then that's just the cruise control doing its job.

Yes. It only does it on cruise. This is the only car I've ever owned where I've felt it do that. The others have been smooth.
 
Yes. It only does it on cruise. This is the only car I've ever owned where I've felt it do that. The others have been smooth.

Just looking through google it seems this is an extremely common "issue" between many different makes/models of vehicles. I wouldn't worry about it.
 
Just throwing this out there, my tb was extremely dirty. So dirty it was having trouble maintaining idle speed. I'm not suggesting cleaning it if it's not extremely dirty, but I'm sure if it was dirty it would have trouble maintaining a speed.
 
No trouble maintaining speed. If I had to liken it to something, I'd liken it to engine braking.
 
Just throwing this out there, my tb was extremely dirty. So dirty it was having trouble maintaining idle speed. I'm not suggesting cleaning it if it's not extremely dirty, but I'm sure if it was dirty it would have trouble maintaining a speed.

very true; cleaning MAF, TB, and running a bottle of lucas through the gas wont hurt and may even get rid of the issue altogether. it is not normal op for it to hesitate. the issue is caused by the 4-5-4 shift parameter and/or the TCC being out of wack due to new/clean parts with old specs or dirty parts. either way, it can be smoothed out with a bit of cleaning described above and/or reprogramming via drive cycle step 10 and the other step i vaguely described in my other post above
 
I, for the life of me, cannot find the post that lays out the drive cycle procedure. Can someone post the link for it here. Thanks.
 
No trouble maintaining speed. If I had to liken it to something, I'd liken it to engine braking.

That is the computer trying to maintain your chosen downhill speed. I'll wager good money that it doesn't do it with the cruise disengaged.

I, for the life of me, cannot find the post that lays out the drive cycle procedure. Can someone post the link for it here. Thanks.

That's because there really isn't one. Ever buy a new car? I've had quite a few and the car NEVER needed a "drive cycle" to operate correctly. I've replaced the DCCV, exhaust system, O2 sensors and the solenoid pack without any issues; just install the parts and go. I had the alternator replaced on 2 of my LSes and also just drove away. If all you want to do is reset the computer, disconnect the battery for at least 10 minutes. That will reset all the "learned" (adapted) parameters to the factory settings.
 
There actually are drive cycles, but none are required. They are used to bring the emissions monitors back to ready as quickly as possible for a mechanic to verify that a repair fixed a problem or so that the car can be emissions tested. Outside of this, there is no need. The car continuously learns, so a few drives after any reset and drive cycle, and it will be back to its old habits.

As was said, none of the new cars that I purchased (including two LSes) went through any drive cycles other than normal driving.
 
There actually are drive cycles, but none are required. They are used to bring the emissions monitors back to ready as quickly as possible for a mechanic to verify that a repair fixed a problem or so that the car can be emissions tested. Outside of this, there is no need. The car continuously learns, so a few drives after any reset and drive cycle, and it will be back to its old habits.

As was said, none of the new cars that I purchased (including two LSes) went through any drive cycles other than normal driving.

to which i say, go check out step 10 and tell me the last time you did that in a 'normal' drive cycle... that tranny sensor was never set correctlyin your car.

the car is highly adaptive when you disconnect the battery, all of the sensors are based on each other in some way shape or form, so to have your car adapting w/o sensors calibrated correctly is silly and results in what i would call 'tics' like the symptom your car is exhibiting. harsh shifting, lurching, even some misfires and lean/rich codes can be caused by improper sensorory input. car is expecting one thing and its getting another and it doesnt know what to do. rule #1 of any database, which is essentially what KAM is, is garbage input = garbage output. if the data in your KAM is resulting in your car doing thigns you dont want it to do, you may just want to get rid of it and start over.

but i think your issues can be corrected by steps 10 and 11. i would try 11 first, then 10 just because its easier. for step 10 find a nice road about 2 or 3 miles long and few stoplights and easy places to turn around. or do it in the right lane of the highway if youre comfortable with people speeding past you
 

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